Electric discharge lamp circuit



Dec. 16, 1941. w. J. sco'rT ELECTRIC DISCHARGE LAMP CIRCUIT Filed June6, 1940 Inventor William J 14 64) His Attorney.

Patented Dec. 16, 1941 ELECTRIC DISCHARGE LAMP CIRCUIT William J. Scott,Rugby, England, assignor to General Electric Company, a corporation ofNew York Application June 6, 1940, Serial No. 339,159 In Great BritainJune 26, 1939 3 Claims.

My invention relates to gaseous electric discharge lamp circuits andparticularly to such circuits which are adapted for use with electricdischarge lamps which at starting require a pre heating of theirelectrodes. For such preheating of the electrodes it is common toprovide the lamp with a short circuiting switch whereby heating currentis drawn from the supply line through the lamp ballast and the two lampelectrodes. The ballast employed must have a minimum impedance for theproper control of the lamp during its normal operation but in certaincases this minimum is too large to permit the heating of the electrodesin as short a time as is desired. It is the object of my invention,therefore, to provide an improved circuit by which the impedance of theballast is decreased when the electrodes are to be heated for thestarting of the lamp thereby to shortenthe starting period. My inventionwill be better understood from the following description taken inconnection with the accompanying drawing and its scope will be pointedout in the appended vclaims.

Referring to the drawing Fig. 1 is a circuit diagram illustrating oneembodiment of my invention, and Fig. 2 is a like diagram showing amodification.

In Fig. 1 of the drawing shows a gaseous electric discharge lamp of thepositive column type comprising a tubular envelope having the spacedelectrodes 2 and 3 therein and containing a gaseous atmosphere such as afew millimeters of a rare gas, for example argon, and a small quantityof a vaporizable metal, such as mercury. The interior surface of theenvelope may, if desired, be covered with a fluorescent material. Theelectrodes 2 and 3 are thermionic being filamentary in form and adaptedto be preheated to an electron emitting temperature before the dischargeis started in the lamp. The lamp is shown connected with the source ofsupply 4 of alternating current which, for example, may be a 60 cycle,115 volt lighting circuit, the connections therewith being representedat 5 and 6. In one of these connections, namely, 5 I have shown the lampballast 1. While this may be in the form of a resistor, I prefer toemploy a choke coil or reactor because of the economy'in operationobtained therewith. I have accordingly represented the ballastas areactor having the core 8 upon which is the winding 9. The winding isprovided with the intermediate tap whereby the winding is divided intothe two parts H and 2, part II being connected directly with one end ofthe electrode 2. The tap connects with the front contact ll of theswitch |5 and the end of the part l2 of the winding connects with theback contact l6 of the switch. The blade of the switch connects with thesupply circuit 4, a suitable control switch ll being shown in thisconnection. Tied to the switch l5 by the insulating link 20 is the lampshort circuiting switch 2| the blade ofwhich connects with one end ofthe electrode 3 and the fixed contact 22 of which connects with theother end of the electrode 2. This switch may be electromagnetic ifdesired, but I prefer it to be thermal. For that reason I haverepresented the switch 2| as a bimetallic strip having the heater 23adjacent thereto by which the strip is caused to warp in a direction toopen the short circuit produced thereby. The heater 23 is shown includedin the connection 6 between the other end of the electrode 3 and thesource 4. It is so constructed and related to the bimetal stripcomprising the switch 2| that when the electrodes 2 and 3 become heatedto an electron emitting temperature the switch 2| will open the shortcircuit across the lamp and thus cause the lamp to start.

When the circuit is energized by the closing of the control switch H,the two switches being in the closed positions illustrated, heatingcurrent is supplied to the lamp electrodes through section II only ofthe ballast reactor. By reason of the relatively low impedance of thissection of the reactor the value of the current supplied to theelectrodes is such as quickly to bring them up to an electron emittingtemperature. When this is reached the switch 2| operates to open theshort circuit causing a discharge to start in the lamp and at the sametime operating the switch I5 to include the section 2 of the reactor aswell as the section II thereof in circuit with the lamp, the impedanceof the entire reactor being that required for the proper operation ofthe lamp.

Instead of switch l5- serving to open circuit the part l2 of the reactorfor the purpose of rapidly heating the electrodes it may, if desired,serve to short circuit that part. Thus the end of part l2 of the reactormay be permanently connected with the switch blade l5 as shown by theline 24 in Fig. 2.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. In combination, a gaseous electric discharge lamp having a pluralityof spaced electrodes therein adapted to be supplied with preheatingcurrent, a two-part reactor connected in a series of one of the parts ofsaid reactor on said preheating current by cutting out said part andcommon actuating means for said switches.

2. In combination, a gaseous electric discharge lamp having a pluralityof spaced electrodes therein adapted to be supplied with preheatingcurrent, a reactor having a two-part winding connected in a seriescircuit with said lamp to be supplied from a source of alternatingcurrent, a switch connected between said electrodes for controlling thepreheating current supplied thereto, means for increasing the supply ofpreheating current to said electrodes comprising a switch arranged inone position thereof to eliminate the eilect of the reactanoe of one ofthe parts of said reactor in reducing said preheating current by cuttingout said part and means for operating said switches substantiallysimultaneously.

3. In combination, a gaseous electric discharge that side of said sourceto which the reactor is connected whereby in one position of the switchthe current of said series circuit is supplied from said source to oneend of said reactor and in another position thereof it is supplied tosaid tap, and means responsive to said preheating current for actuatingsaid switches.

WILLIAM J. SCOTT.

